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Thread: Total alkalinity low, PH OK, add baking soda?

  1. Back To Top    #1

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    Total alkalinity low, PH OK, add baking soda?

    Hello all, we have a 12000 gallon free form in-ground gunite pool that is a little over a month old. Currently running a trichlor chlorinator and keeping an eye on CYA, will go to BBB eventually. Cartridge filter. The water has been crystal clear except for a couple of days after a huge storm blew through and filled it with dirt/ dust (it's cleared again since then). The chemicals have all been holding steady within normal range except for total alkalinity which has been running on the low side of normal (consistently testing in the 50 to 60 range). We were given a drop-based testing kit that tests for total Chlorine, PH and TA. We just got a TF100 kit and as mentioned above everything is within normal ranges except TA. Does adding baking soda increase TA and PH or just TA? We also have an 11' long waterfall and a grotto which is running 1-1/2 hours a day. If you need to see all the TF100 results I'll post them tonight when I get home. The water looks great, so I'm not trying to "fix" any water problems. Thanks!
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    The baking soda will raise both the TA and the pH, but will mostly raise the TA. If you start at a pH of 7.4 and a TA of 55 ppm, then in 12,000 gallons adding 13 cups (130 ounces weight, actually) of baking soda will raise the pH to 7.6 and the TA to 100 ppm. So the rise in pH isn't dramatic.

    The aeration from the waterfall and grotto will outgas carbon dioxide faster causing the pH to rise, but since the Trichlor you are using is acidic, you may be noticing that your pH is somewhat stable in which case what happens is that the TA drops over time. That's how you got to where you are now. In such a situation, adding baking soda every now and then is all that may be needed.

    When you switch to using an unstabilized source of chlorine, such as bleach or chlorinating liquid, you may find that the pH rises faster. You either have to add acid now and then or need to reduce the aeration (run the waterfall less frequently). That's just the tradeoff and is not a big deal since technically using Trichlor is like adding acid anyway, but with Trichlor you are also adding CYA which can be a problem if it gets higher. If your FC level isn't currently at least 7.5% of the CYA level at all times, then you risk getting algae and either need to raise the FC level or use a supplemental algaecide (such as PolyQuat 60).

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  3. Back To Top    #3

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    That's great info and very helpful Richard, many thanks!!! As you guessed the PH has remained very stable. The TA has never been in the normal range though. We did a low PH startup for the first 2 weeks as recommended by the PB, so I was adding acid to keep the PH low. After the initial 2 weeks I quit adding acid and the PH come up into the normal range and has stayed there. The TA has been camped out in the 50-60 range the whole time though. I'll follow your suggestions and bring the TA up with baking soda (over time). Thanks again!
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  4. Back To Top    #4

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    Added 2 pounds of baking soda yesterday and that raised the TA from 50 to 70 (tested today) with no measurable difference in PH. I aded a little less than a pound tonight and will check it again in 24 hours, but it certainly appears that it is doing the trick. Thanks again Richard!
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  5. Back To Top    #5

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    You can stop raising the TA when it gets to 80, if you want, and see how things go from there. Eventually, when you switch to using unstabilized chlorine, you may not want the TA to be high so if you stop now at 80 ppm then you won't have to lower the TA later on.

    I am surprised that your continued use of Trichlor with relatively stable pH didn't have your TA drop over time. Did you add any pH Up even infrequently? That would explain why you haven't seen a drop in TA over time.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  6. Back To Top    #6

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    Thanks, I am shooting for 80 and will hold it there. The pool is only a month old, so there hasn't been much time for the TA to drop. Plus we've had around 5" of rain since it was completed, so there's been some dilution.
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